problem-lawn

Last Autumn I laid a lawn under trees and in shadow a lot of the time, especially this time of year - I did research (badly as it happens) the kind of turf to lay. I used the internet and was duped!

I discovered the turf had been grown on a plastic lace - which I did not discovered until too late to do anything about. To be fair part of the lawn in OK sh and with care and a feed is not too bad and I can live with, but the largest area under the trees is now bare - no grass at all! I've cut out the plastic and now want to 'seed' it - any suggestions from anyone as to what kind of seed and more to the point - when can I do it?